Corey Bailey

           Audio Engineering

GLOSSARIES  RECORDS & TURNTABLES

Anti-Skate The rotational direction of a turntable platter coupled with the angle of the Tonearm causes the stylus, and subsequently the entire Tonearm, to drift toward the center of the record. This “drift” tends to increase as the Tonearm gets closer to the center of the record. There is an adjustment at the base of the Tonearm to counteract this force and allow the stylus to travel in the center of the grove as it nears the center of the record. Not all turntables have an Anti-Skate adjustment. On some turntables, the Anti-Skate adjustment is fixed. Some turntables use a balance weight connected to a fine thread which, in turn, is connected to the Tonearm. Misalignment of the anti-skate adjustment can cause the stylus to apply more pressure to one side of the groove wall which can adversely affect record wear and in extreme situations, affect the fidelity of playback. Cartridge Cartridge, in this case, refers to a Phono Cartridge which is that thing attached to the record playing end of the Tonearm. The cartridge holds the stylus and converts the mechanical vibrations of the stylus to the electrical energy that is amplified by the phono preamp. There are two predominant types of phono cartridges: Moving Coil and Moving Magnet. Moving Coil cartridges are built using tiny coils of very fine wire that are modulated by the stylus. These coils are centered in the field of stationary permanent magnets. Electrical energy is induced into the stationary magnet by the modulating coils. The stationary magnet also has several turns of very fine wire around it forming the coil that connects to the Phono preamp. When first introduced, Moving Coil cartridges were known for their high fidelity. However with advances in technology there is now little, if any, noticeable difference in fidelity between Moving Coil and Moving Magnet designs. A Moving Magnet Cartridge is built just the opposite of a Moving Coil Cartridge in that permanent magnets are modulated by the stylus and electrical energy is induced into stationary coils which, in turn, are connected to the Phono preamp. Moving Magnet cartridges typically have a higher (louder) output than Moving Coil and are generally cheaper to produce. There is a third type of Cartridge known as ‘Ceramic’. This type consists of a piezoelectric crystal that is modulated directly by the stylus. The rapidly changing pressure on the crystal causes a tiny electrical current to be generated which is then amplified by the phono preamp. Ceramic cartridges, while less expensive to produce, suffered form fidelity problems as the output of the crystal is typically non-linear. Produced from the 1950’s through the 1970’s, Ceramic cartridges were found in many of the lower cost systems. Dead Wax This is the area of a record that lies between the last groove of recorded sound and the label. It is the area where the Tie-off groove is and is also where the Matrix number and any other information is placed. Equalization In the audio realm, (particularly professional audio) equalization refers to the deviation of certain frequencies or certain groups of frequencies from their original relationship to each other. The tone controls on your home stereo can be referred to as the ‘equalizer’ section. Adding or subtracting Treble or Bass is the process of equalizing the signal passing through your audio system. With respect to records, it was determined early on that reducing a certain amount of the bass frequencies allowed for more time to be recorded on the disk. This is because the bass frequencies require a wider groove width to be accurately reproduced and there is a finite amount of space on the side of a given disk. Thus, there is a built in base boost in your record preamp to compensate for this. Likewise, it was discovered that increasing the treble frequencies when cutting a disk had the effect of eliminating some of the surface noise when played back using the opposite emphasis or ‘equalization’. So, depending on the type of record being played, there is a specific equalization curve being applied by your record preamp to compensate for the “pre-emphasis” applied during the disc cutting process. Gatefold This is term that started in the early 1950’s with some 45RPM releases and evolved with the LP era. Basically, it is any album jacket that has a hinged cover to house a single record. The purpose being to allow extra space for more text, artwork or both. Double albums are Gatefold by design in order to house both discs. Headshell The Headshell is that hood-like shaped device at the record end of the Tonearm that holds the Phono cartridge. Many Headshell designs are removable allowing for an easy change of the cartridge-stylus combination to accommodate the varying types of record grooves. Lateral Grove Lateral groove refers to the groove being “side-to-side” with respect to the disk. Lateral cut records are monaural or “MONO”. The vast majority of records made since the beginning of record production are lateral cut. Stereo records look like they have a lateral cut groove but the information for each channel is cut into the groove walls where the outside part of the groove contains the Right channel information and the inner groove wall contains the Left channel. A stereo stylus differs from a mono stylus in that it can track both horizontally and vertically because it is reacting to the individual channel information on each groove wall. Here is a link to an excellent representation of how the various styli track a record groove: http://www.vinylrecorder.com/stereo.html   Lead-in This is the groove on the outer edge of a record that leads the stylus into the first track or recording. Linear Tracking This is a unique design of a turntable whereby the Tonearm tracks straight across the record as opposed to the usual arc of a Tonearm that is fixed at one end. Linear tracking turntables work by using a feed screw mechanism that causes the Tonearm to move straight across the record surface at a predetermined speed. The idea behind a linear tracking turntable is to track a record in the same manner as a record cutting lathe which uses a linear mechanism to create the lacquer coated master disc. Matrix Number This is a number, or combination of numbers and letters, that is inscribed (often stamped) into the Dead wax area of a record. Think of it as a catalog number. This number is usually assigned by the record company to keep track of the masters used to press records. It can also be assigned by the pressing plant for the same purpose. Also, in this area, can be found the Dead wax inscription by the Mastering Engineer. Collectors will often use both the Matrix number and Dead wax inscription to determine how collectible the disc may be.   Microgroove Introduced in 1948 by Columbia Records, the Microgroove record boasted a groove width about one third that of the conventional 78 RPM records produced prior to that date. This also heralded the “re-introduction” of the 33-1/3 RPM disk for consumer use which was now manufactured using a vinyl compound. This “new” format boasted better fidelity, longer playing times (almost 3 times longer) and was touted as unbreakable compared to its 78 RPM predecessor. 45 RPM “singles” introduced by the RCA Victor Company in 1949 also incorporated the microgroove format. Platter The Platter is the round platform that the record rests on while being played. The Platter is the driven element in a turntable and the methods of rotating the platter vary from direct drive where the platter is part of the motor, to belt drive, to rim drive where a small motor driven rubber wheel turns the platter from inside the rim. Plinth Plinth is actually an architectural term that refers to the base of a column. However, in record turntable parlance, it refers to that part of the base to which the platter and Tonearm are attached. The plinth is usually isolated from the main turntable base by some sort of suspension. RIAA Curve RIAA is an acronym for Record Industry Association of America. The RIAA Curve refers to a record and playback pre-emphasis or ‘Equalization’ that was standardized for the production of microgroove records in about 1954. It is also known as RIAA Equalization, or the RIAA curve. Rumble Rumble is in an induced low frequency vibration in the turntable platter that can be caused by anything from the platter drive system, to worn bearings, to one of the kids running across the living room. Since rumble is an induced vibration in the turntable platter, it gets directly coupled to the stylus when a record is played and subsequently amplified by your stereo system. Rumble is measured by playing a record with a noiseless groove (no modulation) and monitoring the output of the cartridge. Measured Rumble is generally expressed in decibels as a minus number. Stylus The Stylus is that “needle point” part of the Phono Cartridge which makes contact with the record. The small needle-like shaft sticking out from the Phono Cartridge with the stylus at the very end is called the “stylus Bar”. The stylus itself is a shaped jewel. The jewel is most often a sapphire or diamond and it is finely ground to a conical or elliptical shape which are the most common. There are actually several shapes available for stylus tips and which shape is best for a given application is often the subject of controversy. Tie-off The Tie-off groove is that groove at the end of the last recording on either side of a record. It consists of two parts: The lead-out groove which leads the stylus to the locked groove. The locked grove is a continuous circle designed to keep the stylus from wandering into the label area. The locked groove part of the tie-off also serves to trigger the mechanism of automatic record changers by virtue of its small diameter. The lead-out groove and the circular locked groove are usually silent however, some inventive artists have used this groove to create a loop of audio. Tonearm The Tonearm is easily identified as that pivoted arm or lever that holds the Phono cartridge over the record being played. The Tonearm has two important adjustments available: A counterweight that allows for adjustment of the Tracking force of the stylus and an Anti-skate adjustment to keep the stylus centered in the groove as the record plays closer to the center of the record. Also see Linear Tracking. Tracking force Tracking force is the downward pressure applied to the stylus to keep it in the groove of the record. Tracking force is calibrated in grams and is adjustable by virtue of a weighted counter-balance at the opposite end of the tonearm from the stylus. This is a very important adjustment. Too little tracking force and the stylus will slip out of the record groove, possibly damaging the record. Too much tracking force can damage the record, the stylus or both. Tracking force is measured using a specially designed and constructed balance beam scale that is placed under the stylus with the platter at rest. There are also some specially constructed electronic scales for this purpose. Transcription Disc Transcription discs were direct-to-disc recordings made from live radio broadcasts. The discs were usually 16 inches in diameter and were 33-1/3 RPM. While these discs were made at the same speed as vinyl LP's produced later on, the groove width was similar to 78 RPM discs. Quite often, these recordings served as masters for short runs of disks to distribute syndicated programming to individual radio stations. Turnover Frequency When record masters are cut on a recording lathe, a certain amount of “Pre- emphasis” is applied to the audio being inscribed in the disc. This Pre-emphasis amounts to reducing the bass frequencies and increasing the treble frequencies (See: Equalization). The amount of Pre-emphasis and the specific frequencies involved, depended on the type of record being produced. 33-1/3 and 78 RPM records for example had different amounts of Pre-emphasis applied at different frequencies. The turnover frequency (or frequencies) are that part of the audio spectrum not affected by the Pre-emphasis curve being applied. Vertical Grove or “Hill and Dale” The predominant method for record grooves starting from the very beginning of record production was lateral grove or “side-to-side”. There were however, a few discs whereby the grove was cut vertically. This type of record groove is also known as “Hill and Dale”. Some of the early recordings that were produced with vertical cut grooves were Phonograph Cylinders, Edison Disc Records, Pathé Disc Records, and a few Transcription discs. One cannot play a vertical cut record with a stylus designed for lateral groove records. It is possible however, to modify the wiring scheme of a stereo stylus to play a vertical grove because a stereo stylus can move vertically as well as laterally. References Howard M. Tremane, “Audio Cyclopeia” Second Edition, Howard W. Sams, 1973  Rudolph F. Graf, “Dictionary of Electronics” Howard W. Sams, 1974 Glenn D. White, “The Audio Dictionary” University of Washington Press, 1987 Wikipedia, http://www.wikipedia.org/ Return to TOP of page © Corey Bailey Audio Engineering